Adrenal regeneration hypertension (ARH) is a form of experimental hypertension induced by injuring the adrenal glands of properly sensitized rats. The etiology is unclear, but an unknown mineralocorticoid has been postulated to be the cause of the hypertension. We have described the existance of an unknown compound with mineralocorticoid radioreceptor activity in the urine of rats with ARH and have isolated and identified it to be 19-nordeoxycorticosterone (19-nor-DOC). We have synthesized it and a tritiated tracer which we are currently utilizing to develop a radioimmunoassay for its measurement in blood and urine. Injection of 19-nor-DOCA into rats elicited a hypertensive response. We propose to measure DOC and 19-nor-DOC plasma concentrations throughout the development of ARH to study its role in hypertension. The effects of ACTH and angiotensin II administration and circadian variations in plasma DOC and 19-nor-DOC will be examined. In addition, the biosynthetic pathways will be studied in the adrenal gland to identify precursors and mechanisms of its biosynthesis.